Connected to Wifi but can't access internet

please help. my computer (Toshiba-satellite) says I am connected to local and Internet but I can't get online at all.
Every program and browser I try to open stops working and I get a message from Microsoft windows (Vista) saying a problem caused the program to stop working correctly windows will close the program and notify you if a solution is available. I have tried every suggestion I can find and just about every form and nothing has worked if anyone has a clue or a solution to this problem please let me know. I don't know what else to do.